Conventionally, the contact probe used in contact probe assemblies for electrically testing electroconductive patterns of printed circuit boards and electronic components in general comprises an electroconductive needle member, a tubular holder slidably receiving the needle member, and a coil spring for urging the forward end of the needle member out of the tubular holder so that the forward end of the needle member may be brought into contact with an object to be tested with a certain elastic force pushing the needle member against this object.
As a type of such a contact probe, there are known those employing a pair of needle members which are received in two ends of a tubular holder and elastically urged by a compression coil spring away from each other. One such contact probe is disclosed in Japanese utility model laid-open (kokai) publication No. 60-154868. A contact probe of this type having two moveable accessing ends is typically employed for temporarily connecting the circuits of two circuit boards, which are to be ultimately connected with each other during one of the subsequent fabrication steps, for testing purpose. According to this structure, the electric connection between the two accessing ends is accomplished by a central conductor wire directly connected between the two needle members, for instance by soldering or brazing, the electric resistance between the two accessing ends may be kept both low and stable.
However, according to this structure, the central conductor wire is required to flex, bend or otherwise deform as the two needle members move toward and away from each other. Therefore, when the tubular holder is required to have a very small diameter, typically to the end of densely arranging a number of contact probes in a limited area of a contact probe assembly, the tubular holder is required to be long enough to accommodate flexing or slackening of the central conductor wire, and this is detrimental to the compact design of the contact probe assembly.